用指定方法解方程:(1)x 2 +4x-2=0 (配方法)(2)x 2 +3x+1=0 (公式法)(3)4(x+1) 2 =9 (2x-5

2024-12-23 14:39:34
推荐回答(1个)
回答1:

(1)∵x 2 +4x-2=0,
∴(x+2) 2 =2+4,
即(x+2) 2 =6,
∴x+2=±
6

∴x 1 =
6
-2,x 2 =-
6
-2;
(2)∵x 2 +3x+1=0,
∴x=
-b±
b 2 -4ac
2a
=
-3±
9-4
2×1

∴x 1 =
-3+
5
2
,x 2 =
-3-
5
2

(3)∵4(x+1) 2 =9(2x-5) 2
∴2(x+1)=±3(2x-5),
∴x 1 =
17
4
,x 2 =
13
8

(4)∵x+3-x(x+3)=0,
∴(x+3)(1-x)=0,
∴x 1 =-3,x 2 =1.